The filibuster might seem like payback for Democrats after Republicans refused to consider the nomination of then-President Obama’s Supreme Court nominee, Merrick Garland, for 293 days starting last year. Unlike Republicans last year, however, Democrats don’t have all that much power. They aren’t in the majority — and McConnell has strongly hinted that he could seek to eliminate the filibuster for Supreme Court picks if Gorsuch can’t get 60 votes. Across a variety of surveys, moreover, a plurality of voters think the Senate should confirm Gorsuch, although a fair number of voters don’t have an opinion either way. Therefore, Democrats’ political endgame is unclear.

Gorsuch is quite unpopular with liberal voters, however: By a 61-15 margin, they oppose his confirmation, according to a YouGov poll last week. Thus, the planned filibuster may simply be a sign of the liberal base’s increasing influence over the Democratic coalition. The share of Democrats who identify as liberal has steadily increased over the past 10 years. According to the recently released Cooperative Congressional Election Study, 53 percent of Democratic voters identified as liberal last year. Until recently, it was rare to find surveys that showed liberals made up a majority of the party.

But to some extent, that 53 percent figure understates the case. The CCES also asked voters about whether they’d engaged in a variety of political activities, including donating to a candidate, attending a political meeting, working on behalf of a campaign or putting up a political sign. Among Democrats who’d done at least one of those things — a group I’ll call “politically active Democrats” — 69 percent identified as liberal. These were some of the voters who helped propel Bernie Sanders to almost two dozen primary and caucus victories last year.

Oftentimes these liberals are found in states where you might not necessarily expect them — such as in the Mountain West, which was a strong region for Sanders last year. According to a regression analysis conducted on the CCES data, the proportion of politically active Democrats who identify as liberal is larger in states where candidate Trump fared poorly. But controlling for that, it’s also larger in states that have more white voters, and more college-educated voters. And it’s larger in the West than in the other political regions of the country. In the table below, I’ve estimated the share of politically active Democrats in each state who identify as liberal. Since the sample sizes for some states are small, the estimates are based on a blend of the raw polling data from the CCES and the regression model I described above.1

SHARE OF POLITICALLY ACTIVE DEMOCRATS THAT IDENTIFY AS LIBERAL

STATE

DEM SENATORS UP FOR RE-ELECTION

POLL-BASED ESTIMATE

MODEL-BASED ESTIMATE

BLENDED ESTIMATE

D.C.

87%

77%

84%

Idaho

92

74

82

Utah

85

74

80

Washington

Cantwell

78

76

78

Minnesota

Klobuchar

78

74

78

Oregon

77

78

77

New Hampshire

81

71

76

Vermont

Sanders

78

75

76

Montana

Tester

73

77

76

Alaska

84

71

75

New Mexico

Heinrich

76

73

75

Maine

King

78

69

74

Arizona

75

70

74

Massachusetts

Warren

75

72

74

Connecticut

Murphy

75

72

74

Rhode Island

Whitehouse

74

73

73

Virginia

Kaine

73

68

72

California

Feinstein

72

74

72

Michigan

Stabenow

73

69

72

Indiana

Donnelly

73

68

72

Wyoming

83

67

72

New York

Gillibrand

72

71

72

Iowa

72

71

71

Illinois

71

70

71

South Dakota

82

67

71

Colorado

69

75

70

Nebraska

73

67

70

Arkansas

78

59

70

Florida

Nelson

69

66

69

Nevada

68

69

69

Tennessee

70

63

68

Pennsylvania

Casey

68

70

68

Delaware

Carper

63

72

68

Wisconsin

Baldwin

67

72

68

Ohio

Brown

68

68

68

Kansas

64

70

66

Mississippi

73

54

65

North Carolina

64

66

65

Texas

64

63

64

New Jersey

Menendez

63

67

63

Oklahoma

63

61

63

Louisiana

61

66

63

North Dakota

Heitkamp

51

66

61

Kentucky

60

64

61

Hawaii

Hirono

43

71

61

Missouri

McCaskill

60

65

61

Alabama

61

57

59

Maryland

Cardin

58

64

59

West Virginia

Manchin

49

67

57

South Carolina

51

59

54

Georgia

49

61

51

Where is the Democratic base most liberal?

Source: Cooperative Congressional Election Study

It’s not surprising that Washington, Oregon and Vermont are places where the liberal wing of the Democratic base dominates. But Idaho, where I estimate that 82 percent of politically active Democrats identify as liberal, and Utah, where I estimate that 80 percent do, also rate near the top. It’s not that Idaho and Utah are blue states, obviously; they’re among the most Republican in the country. Nonetheless — perhaps because a lot of moderate voters identify with the GOP in these states — the few Democrats that remain are overwhelmingly liberal.

The same phenomenon holds in Montana, where I estimate that 76 percent of politically active Democrats are liberal. That may help to explain why Sen. Jon Tester of Montana says he will vote against Gorsuch, even though he faces a tough general election campaign next year. Whether or not Democrats would issue a primary challenge to Tester, who has generally sided with the party on key votes, is questionable. Nonetheless, he’ll be relying on his base for money, volunteers and a high turnout on Election Day. In Montana, the conservatives are conservative — but the Democratic base is fairly liberal also.

By contrast, Democratic Sens. Heidi Heitkamp of North Dakota and Joe Manchin of West Virginia, who will vote to confirm Gorsuch, are on somewhat safer ground. Some 61 percent of politically active Democrats identify as liberal in North Dakota, while 57 percent do in West Virginia, according to this estimate. Those figures are almost certainly higher than they would have been a few years ago. But Heitkamp and Manchin probably face more risk from the general election than from a loss of support among their base.

Nor is the Democratic base all that liberal in the Mid-Atlantic region, including states such as Maryland, Delaware and New Jersey. Instead, even the party activists in these states can have a moderate, pro-establishment tilt. That may explain why senators such as Chris Coons of Delaware and Robert Menendez of New Jersey were slow to announce their positions on Gorsuch before eventually deciding to oppose him.

Footnotes

The regression model is taken to be equivalent to 35 interviews. That means it gets little weight in states where a large number of politically active Democrats were polled by the CCES, but more in states such as Wyoming where there were few interviews conducted.

Nate Silver is the founder and editor in chief of FiveThirtyEight. @natesilver538